The present relates to a variable stator vane for a gas turbine engine, more specifically such a variable stator vane having a separate guide disk in order to render the fabrication of the stator vane more economical.
Variable stator vanes for gas turbine engines are well known in the art and, as illustrated in FIGS. 1 and 2, comprise vane assemblies 1 having a stator vane 2 mounted in the casing 3 of the gas turbine engine. A control pivot rod 4 pivotally supports the upper end of the vane 2 by passing through a bore 5 defined in a boss 6 extending outwardly from the casing 3. In order to transmit and distribute the stresses from the vane 2 to the casing 3, a disk portion 7 is formed on the upper and of the vane 2 such that it extends into a recess 8 defined by the inner surface of the casing 3. The relatively large area of contact between the disk member 7 and the recess 8 minimizes the stress concentrations between the vane 2 and the casing 3.
As is typical, the disk 7 is formed integrally with the vane 2 and the control rod 4. These elements are machined from one piece of a steel or an alloy ingot, usually by electrochemical machining techniques. As a rule, the diameter of disk member 7 is generally equal to the chord "c" of the vane 2. Thus, it is necessary to start the machining process with an ingot that has a width at least equal to the chord of the vane and a thickness at least equal to width of the member 7. Quite obviously, this results in a great waste of the steel or alloy material and a consequent increase in costs of the fabrication of such stator vanes. French Patent 2,599,785 discloses a vane structure wherein the disk member is formed in one piece with the vane.
It is also known to form a movable vane assembly by separately fabricating the disk and subsequently brazing or welding it to the vane member. This technique is illustrated in U.S. Pat. No. 2,955,744 to Hemsworth and U.K. patent application 2,027,811A. While such techniques lower the cost of fabrication, there is always the danger of the failure of the braze or weld which may cause catastrophic failure of the gas turbine engine.